|Head-Down Display [HDD]
|Electronic Head-Down Display (EHDD)
|Airborne Display [ADD]
|Year of Manufacture:
Width (mm): 170
Height (mm): 193
Depth (mm): 410
Weight (g): 8,160
|Rack RAA08 [Main Store]
The Electronic Head Down Display (EHDD) was fitted to the pilot’s cockpit of the Air Defence Variant (ADV) of the Tornado. On the ADV the ground mapping radar display is not required, since all radar displays are basically synthetic. The pilot has the EHDD which is an extension of the Navigator’s TVTab display system. This gives the pilot full access to all data available to the Navigator and in addition provides head-down attack information and steering for interception.
The unit has three pushbuttons and a rotary switch for mode selection and a rotary Brightness control.
The EHDD uses a high brightness green monochrome Cathode Ray Tube made by Rank Brimar with a contrast enhancement filter. (It was initially specified to have an automatic brightness control operated by monitoring the brightness of top and bottom scan lines outside the general image frame. Optical sensors were employed to measure the brightness of the few scan lines but it was found to be unworkable in its form. A more conventional method of measuring the brightness by measuring the CRT cathode current was resorted to and its physical equation replicated with analogue multipliers and log amplifiers to create the desired function. Note: Courtesy of Steve Pink)
Production Units had a bezel with photosensor slots at the sides; these were always a feature of the EHDD, so the bezel on this EHDD is probably an engineering part for bench use only. The deliverable contrast enhancement filter glass was prone to damage and delamination, and kept out of harm's way until actually needed. Development units had a mode called LANCE, (seen against the right-hand knob, which is missing) and this was changed to ATK for production units.
The -01 configuration confirms this as one of the early development units; variants certainly went up to -20. This unit has Serial Number 012 so would have been built for the Tornado ADV somewhere between the first flight of the aircraft in 1979 and entry into service in 1986.
The Waveform Generator for the EHDD produces synthetic symbols by a process called a time-shared digital technique. This gives high accuracy and avoids the ‘staircase’ effect found in raster generated graphics.